Mechatronic system and method for positioning bolts in order to provide a frame with a reconfigurable surface using memory effect actuators

ABSTRACT

The invention relates to a reconfigurable computer-controlled system based on the positioning of bolts. A greater density of bolts per unit area increases the variety of figures or shapes that can be defined by a frame or tool used in the industry, such that it is no longer necessary to construct rigid surfaces with each change made to the shape of the product to be produced or surface to be formed. The use of the memory effect material as an actuator in the reconfigurability mechanism is the key to the success of the reconfigurable system and the control system owing to the permissibility of small bolts which can be adapted to standard sizes and shapes. The invention also relates to the application of the mechatronic system which uses the positioning of bolts for the reconfigurability of surfaces in order to manufacture and shape materials.

FIELD OF INVENTION

A mechatronic system having a function to create a rigid and reconfigurable surface to adopt complex three-dimensional profiles is disclosed. A method to control the shape of a reconfigurable surface and a use procedure are also introduced. The system may be used as a metal or plastic sheet forming die and also as a positioning guide.

BACKGROUND

It is known from state of the art that in 1900 appears an idea of a shaping reconfigurable die, but it is until 1923 that William and Skiner registered a patent for “Spring Forming Devices” (U.S. Pat. No. 1,465,152) wherein a two-dimension device to form bellows was developed. This device consists of two manual-adjustment bolt columns smoothly distributed. Afterwards in 1931, Hess patented a kit of dies with highly dense elements (U.S. Pat. No. 1,826,783) used for metal sheet stamping. In 1943, Walter takes William and Skiner's idea and expands said die up to three dimensions by adding multiple bolt columns to conform a metal sheet, the bolt layer being opposed each other and with manual type adjustment (U.S. Pat. No. 2,334,520).

In 1969, Nakajima publishes in the Mechanic and Engineer Japanese Society Bulletin, a development for a vertically oriented, re-configurable automatic die, with round bolts and positionable needles, which are mounted on the head of a numerical control turning machine to create serially the shape of a die. In 1973 Wolak J., under the Boeing company sponsorship, carried out a preliminary study of a variable surface generator to be used as a stretching forming die, but the idea was abandoned due to the lack of rigidity in the adjustable bolts.

By late 70's and early 80's, inventor David Hardt from Massachussets Institute of Technology develops a prototype of a re-configurable die by using computer-controlled servomotors for each individual actuator. In 1980 a discrete die, quite similar to Walters's design was also developed, except that each bolt could be automatically adjusted by computer through individual servomotors, with separated bolts each other (U.S. Pat. No. 4,212,188). Massachussets Institute of Technology also develops between 1985 and 1991 a shaping re-configurable die, this design automatically adjusted the die shape row by row and later making a rigid die, through a grasping mechanism. Later in 1991, Finckenstein and Kleiner developed a numerical control flexible machine with square bolts for deep die-pressing. In 1997 an article was published in “AEROSPACE AMERICA” magazine from a researcher, Flinn, E. D, reporting that DARPA (Defense Advanced Research Projects Agency) sponsored a program of re-configurable tools for flexible manufacturing, leaded by Northrop Grumman Corp company, since aerospace industry requirements demand low volumes and an unpredictable demand which requires a reduction in tooling manufacturing costs and times. This die is activated by automatically controlled motors through a computer and being used to adjust bolt height. Inventor Im, Y.-T in 1998 developed a control system for a controlled re-configurable die, but this uses hydraulic cylinders.

In 1998 Walczyk, D. F., and Hardt, D. E developed a die for shaping by using computer-controlled hydraulic actuators, consisting of square bolts which allow to shape sheet and compound materials. Where Walczyk et al., demonstrate that a discrete die may be actuated by means of hydraulic cylinders. In 2002 Papazian et al., together with the United States Air Force Research Laboratory and Warner Robins Air Logistics Center, already developed an activated re-configurable systems with servomotors and computer-controlled, this die having a system which reduced even more the re-configurability time, thus increasing the productivity thereof. However all the previously mentioned patents, as well as the technological developments have a problem in common, the same being characterized by a very large bolt size in this kind of tooling, which is a limitation since only allows a material shaping with very coarse geometry. Another restriction regarding to bolt size is the manipulating actuator, these devices using servomotors and/or hydraulic cylinders.

Therefore the new invention herein proposed, a mechatronic system reconfigurable for shaping materials, significantly reduces the bolt size achieving an increase in bolt density per area unit to provide a large amount of pieces to be manufactured. Additionally, servomotors and hydraulic cylinders are substituted, by functional materials, those which are known as memory effect materials, these materials serve for actuating actuators, thus considerably reducing the size thereof.

However the system may have a number of applications; as a guide for positioning, changing surface or for shaping the generated surface; a sheet for any pressure form, whether by a similar tool, by heat, by water, by oil, etc. The main feature of the mechatronic system is that each bolt is independently actuated, and that its position may be controlled to adopt any desired surface; which gives to system the unique re-configurability features, those which are as fine as the bolt smallness and amount, which would be added to the mechatronic system. Control and movement of each bolt is carried out through a transmission mechanism and an actuator with a memory effect material in the shape of a wire or a plate.

BRIEF DESCRIPTION OF FIGURES

FIG. 1. Block diagram of a mechatronic system to shape a re-configurable surface

FIG. 2.1. Bolt drawing.

FIG. 2.2. Set of bolts for a reconfigurable die

FIG. 3.1. Original position of the basic performance of a bolt with memory effect actuator.

FIG. 3.2. Wire contraction position and bolt rise with a memory effect actuator.

FIG. 3.3. Stand-by position of another signal for bolt basic performance with memory effect actuator.

FIG. 4. Drawing of an individual bolt with thread

FIG. 5. Transmission mechanism of longitudinal movement

FIG. 6. Transmission mechanism section

FIG. 7. General diagram of a mechatronic system control method

FIG. 8. Detailed diagram of a mechatronic system control method

DETAILED DESCRIPTION OF INVENTION

The present invention refers to a mechatronic system and a method for positioning bolts to provide a re-configurable surface to a chassis by means of memory effect actuators. In FIG. 1 the mechatronic system comprises a data processing unit (1), an electronic control unit or controller (2), which is supplied by a power source (3) and the controller is connected to a set of wire actuators (4), characterized by its memory effect and its reaction to heat. The set of actuators (4) is connected to a transmission mechanism (5) of a longitudinal-cross-sectional movement which makes to move each bolt which together form a chassis, with bolts, named reconfigurable die. (6). These bolts are matrix-like arranged and being controlled by a longitudinal-cross-sectional movement transmission mechanism (5).

In FIG. 1 the processing or computer unit is used to program a three-dimensional product design or drawing (desired to be manufactured as well as to execute a control program). The electronic control unit (2) is in charge of sending a signal to activate actuators (4) and thus moving the bolt or bolts, upwards or downwards. In order to change the surface geometry from the die, the set of bolts in FIG. 2.2 may be needed to be of a square shape, such as shown in FIG. 2.1, which may be varied in height, thus having a variable surface in three dimensions to give a shape to sheet products with the desired Figure. Actuators which are commonly used in reconfigurable die systems have a minimum of 1 inch; which occupies a considerable space. However, with this invention the actuator is minimized, thus reducing the size at least in 75%.

This reduction is achieved by using advanced materials such as memory effect materials. The commercial material with the best properties for the desired application is a nickel-titanium alloy (NiTi), since this material in a wire shape may be used as an actuator to provide the required reconfigurability to the die. In FIG. 3.1, the basic bolt performance is shown with the memory effect material, where the extended NiTi wire may be observed without applying any current.

In FIG. 3.2 the basic bolt performance is shown when current is applied, the wire is retracted and the bolt is raised.

In FIG. 3.3 the basic bolt performance is shown with the memory effect material when upon removing the electric current, the spring extends the NiTi wire by returning to its original position.

In FIG. 4, a threaded individual bolt is shown providing the die reconfigurability, which requires a transmission mechanism that rotates a threaded nut or cylinder so that the bolt moves upwards or downwards.

FIG. 5, shows an upward longitudinal movement transmission mechanism (the downward one is similar and being arranged in the bottom part of this mechanism): the bolt (1) is attached to a guide plate (2) and a rotating cylinder (3), which is attached by a support plate (4). The transmission mechanism comprising the crown gears (5) and (6) is in charge of transmitting rotation to the cylinder (3) (a slope opposite to the crown gear makes rotation to change direction) and is attached through a plate (7). The crown gear (6) is activated by a NiTi wire with memory effect (8). The NiTi wire is connected to a transmission bar (9) and having and insulator (10). The system has in its axis, a central wire (11), which provides linearity and a vertical movement. The bolt requires to move downwards a similar system to the one disclosed, though in a different direction in the transmission crown gear (12) arranged in the bottom part.

FIG. 6 shows a detail of a transmission mechanism where we can see the crown gears (1) and (2) and its coupling to transmit rotation to the cylinder moving the bolt, the crown gear (2) is activated with the memory effect material (NiTi), the wire is activated by current pulses, thus having a controlled advancement, the bolt is moved depending on the advancement which is selected by the bolt nut, when being a fine thread advancing in a lower ratio than a coarse thread. By following this sequence each bolt is configured and thus the remaining die, depending on the application, that is, whether used for termoforming, for sheet forming, for hydroforming, etc. Die design and its attachment elements will depend on that.

Description of the Mechatronic System Control Method with Application to Material Shaping.

The method or control logics for die reconfigurability and each bolt movement is programmed in a computer or workstation. In FIGS. 7 and 8 the control method is described consisting of the following steps: Step I. Positioning order algorithm for each bolt. This consists of; (a) product design or drawing to be manufactured in three dimensions, (b) punching die or mold design from product dimensions and design rules, (c) computer simulation for shaping process and die design optimization and (d) definition of a bolt row or column which starts the positioning movement. Step II. Conversion (Bolt distance)-(Electric pulse). This consists of; (a) dot discretization on die surface matching with die bolts and (b) identification of each dot through P_(i,j) coordinates (X,Y,Z). Wherein i and j represent the bolt identification within the reconfigurable die and X, Y and Z, represent coordinates for each bolt including its height on die surface. Once coordinates for each bolt and height on die surface are calculated, they are stored in a computer and sent to a control unit where each coordinate is transformed in electric pulses. Step III. Electric pulse output to each bolt or group of bolts. This consists of controlling the distance that each bolt must go upwards or downwards, to provide the desired shape through the required electric pulses. Control logics may be set out for each individual bolt. The used software allows, depending on the given pulses, to reach the right height, to store all this information and to contain a restart function wherein, upon completing the manufacturing process, the dies goes back to its original position, that is; that all bolts remain in coordinates to be able to start another different shape therefrom. 

1. A mechatronic system for bolt positioning with a data processing unit characterized by an electronic control unit controlling a set of wire actuators, distinguished by their memory effect and their reaction with heat. The set of actuators is connected to a longitudinal-cross-sectional movement transmission mechanism which moves each bolt which altogether forms a chassis, named a reconfigurable die.
 2. A mechatronic system for bolt positioning according to claim 1 characterized in that said reconfigurable die comprises and an unlimited small bolt number activated by a longitudinal-cross-sectional movement transmission mechanism, an elevating and lowering system for each bolt and an electronic control unit. This die may get a surface with any geometric shape; according to the control order or positioning program thus being reconfigurable for multiple uses and applications.
 3. A mechatronic system for bolt positioning according to claim 1 characterized in that said longitudinal-cross-sectional movement transmission mechanism comprises: a notched crown gear system which design define as the rotation direction and whereby the bolt upwards and downwards movement and the notched crown gear assembly activation by means of memory effect wire actuators.
 4. A mechatronic system for bolt positioning according to claim 1 characterized in that the memory effect wire material actuators are electrically connected so that they are heated upon receiving electric power. With the reached and suitable controlled temperature, the wire is retracted and allows the crown gear rearrangement and a spring distorts again the wire to put it in an actuator condition and continuing with bolt upwards movement in case of receiving an electric signal. Particularly, the spring elongates the wire, promotes crown gear assembly and thus, a cross-sectional movement from the rotation cylinder which moves the bolt.
 5. A mechatronic system for bolt positioning according to claim 1 characterized in that the electronic control unit is conformed by an electric circuit which supplies electric power to activate the memory effect wire material, providing time to transmit movement and continuing in repeated and controlled cases with bolt upwards or downwards movement, wherein the control unit is interconnected to a computer to receive the upwards or downwards movement signal depending on die and bolt design.
 6. A mechatronic system for bolt positioning according to claim 1 characterized in that material shaping is carried out on a surface comprising small adjoining bolts using a material in any physical state (liquid, solid or paste), in any shape (plate, sheet or amorphous) and in any material (metal, polymer, ceramics or composite).
 7. A mechatronic system for material shaping according to claim 1 characterized in that gravity, hydraulic, pneumatic or mechanic forces may be used as compressive forces onto forming materials, to reach permanently the die geometric shape.
 8. A mechatronic system control method for material shaping characterized by a three-dimensional drawing of required piece (virtual positive), a three-dimensional design of preform-definitive forming dies, a computer simulation for shaping process, a die design optimization, a dot discretization on die surface matching with die bolts and an identification of each dot through coordinates. The method or control logics for die reconfigurability and movement of each bolt are programmed in a computer or workstation. The control method consists of the following steps: Step I. Positioning order algorithm for each bolt. This consists of; (a) product design or drawing to be manufactured in three dimensions, (b) punching die or mold design from product dimensions and design rules, (c) computer simulation for shaping process and die design optimization and (d) definition of a bolt row or column which starts the positioning movement. Step II. Conversion (Bolt distance)-(Electric pulse). This consists of; (a) dot discretization on die surface matching with die bolts and (b) identification of each dot through P_(i,j) coordinates (X,Y,Z). Wherein i and j represent the bolt identification within the reconfigurable die and X, and y Z, represent coordinates for each bolt including its height on die surface. Once coordinates for each bolt and height on die surface are calculated, they are stored in a computer and sent to a control unit where each coordinate is transformed in electric pulses. Step III. Electric pulse output to each bolt or group of bolts. This consists of controlling the distance that each bolt must go upwards or downwards, to provide the desired shape through the required electric pulses. Control logics may be set out for each individual bolt. The used software allows, depending on the given pulses, to reach the right height, to store all this information and to contain a restart function wherein, upon completing the manufacturing process, the dies goes back to its original position, that is; all bolts remain in coordinates X=X₀, Y−Y₀, and Z=Z₀, to be able to start another different shape therefrom. 